Add the Initial commit for the GitHub Action

[jonathanio]

Add all the code, documentation, and automation for this GitHub Action for running terraform-docs.

[github-actions]

sh-checker report

To get the full details, please check in the job output.

shellcheck errors

'shellcheck ' returned error 1 finding the following syntactical issues:

----------

In tests/arguments.bats line 137:
  export OUTPUT_FORMAT="json"
         ^-----------^ SC2030 (info): Modification of OUTPUT_FORMAT is local (to subshell caused by @bats test).

For more information:
  https://www.shellcheck.net/wiki/SC2030 -- Modification of OUTPUT_FORMAT is ...
----------

You can address the above issues in one of three ways:
1. Manually correct the issue in the offending shell script;
2. Disable specific issues by adding the comment:
  # shellcheck disable=NNNN
above the line that contains the issue, where NNNN is the error code;
3. Add '-e NNNN' to the SHELLCHECK_OPTS setting in your .yml action file.

shfmt errors

'shfmt --indent 2 --binary-next-line --case-indent --simplify' found no issues.